Normal incidence second-harmonic generation in L-valley AlSb/GaSb/Ga1−xAlxSb/AlSb stepped quantum wells

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Abstract
A novel mechanism is proposed for surface‐emitting second‐harmonic generation at normal incidence using L‐valley intersubband transitions in AlSb/GaSb/Ga1−xAlxSb/AlSb stepped quantum wells. The calculations indicate that second‐harmonic susceptibilities of at least 9×10−8 m/V should be achievable under double resonance conditions, which is comparable to the best obtainable in GaAs/Ga1−xAlxAs systems for realistic propagation angles (e.g., 45°). Besides the advantage of normal‐incidence geometry, the large L‐valley conduction band offset between GaSb and AlSb enables doubling to frequencies spanning the entire midwave infrared spectral region.